Manufacture of fine refractory-metal wires.



F. BLAU. I

MANUFACTURE OF FINE REFRACTORY METAL WIRE S.

' APPLICATION r'||.:n JAN- 31. 1912.

1,157,288. Patented Oct.19, 1915;

Figl. Z

MW lnvehtorz Fritz BLau,.

His Attorneg.

To all whom it concern:

rnrrz nmu, or f mmvm sexism, assreuon mo; semen-anaemic rcomm,-a-conroaarron or new-roan, a V v I Be [it'known that I, Dr. FnrrzBrno, a subject of the Emperor of Austria-Hungary, residing atCharlottenburg, Germany, have invented 'certain new and usefulImrovements in the Manufacture of Fine efractory-Metal Wires, of whichthe following is a specification.

-My invention relat to refractory metal. *wire and ribbon and to itsproduction.

By my process of manufacturetungsten filaments or wires can be producedof a fineness and uniformity greatly superior to anything-heretoforemade or obtainable in any way, and this wire is of remarkable uniformityof section for any length desired and of perfectly uniform surface;indeed, extremely small diameters for which the well known Wollastonprocess entirely fails can readily be obtained. in any "desired,lengths. Moreover, the process is easily carried out, and even when thewire is not reduced below what has hitherto been the extreme limit offineness, the production of tungsten wire (especially ofthe finersizes)is. rendered very much easier and cheaper. Other advantages and valuableresultsobtainable through my invention will hereinafter be referred toor be apparent.

It mayhere be particularly mentioned that by the employment of myinvention tungsten lamps of 16 candle power orless adapted for operationwith an efiiciency of about one watt per Hefner candle at such highvoltages as*220 or more may be produced very readily, whereas heretoforeit has been diiiicult or impossible to make such lamps, and even Idifiicult to produce 16 candle power lamps having tungsten wirefilaments for 110 volts and thelikel- According to my invention, atleast a tungsten wires or'filaments' of the desired finenessare finallyobtained is efi'ected chem- 'ically. It is not, however,;necessa ry thatthe wires or filaments consist of chemlcally pure tungsten, but theymaycontain small quantities of foreign componentsfdor example, phosphorus;or refractory,-. ox ids (lime, thorium). Indeed, theseadmixturesmilitate against the well-known; crystalline structure characteristic ofordinary tung- V sten metal,-which' interferes with the chemicaltreatment just referred to,-'-and so 5 Specification oi Letters Patent,I

are 'eyfen useful in my process as a meansof securing filaments 'or wire-without In my process, the crystalline of .the reduction in sizebywhich "then not only. are the ab preserved in the chemical orelectric-chemicalreducln process, but the diiferences become mumnnrnecronv -mnranwmns. p

: Patented oer; 19; Applicationnled'lanuaryfl;1912. iserialiqaigfle.

structure.

structure of ordinary tun sten. metal is got-j V rid of before the metais subjected to chemical treatinent, which may be done by" mechanicalwcrln'ngf of the metal while hot, as set forth in great detail No.23,499 of 1909. 1

in British Patent 7 The tungsten metal which has been de- .prived of1ts"cryst a llinestructure .by mech anical working in a heated conditionmay rolling or drawing and then' subjectedto the action of chemicalmeans which (acting 7'0 .part ofthe mass of the wire or ribbon. The

upon the surface) removes a considerable wire may thus be drawn toasdiameter of about 5 /100 to 3/100millimeters-and the reduction in sizecarried'on chemically after that. Drawing to the diameter just menof"the fact that the manufacture of the:

,bored diamonds. necessary. for the very] "be brought to a very smalldiameter by smallest I diameters is no longen possiblaj Thus the secondpart of theprocess comes becomes uneconomical or fails.

Chemical treatment of the wire may also 'be carried out in severalstages withintervening drawing operations. This has the advantageofreducing the numberof dies required andj-the amount of die wear, as;

"into use where the ifirst part of the process;

well as various'oth'er advantages Furthermore,- the chemical treatmentof the wire 7 7 cannot well be continued uninterrupted so far-that thewire is brought'to a verysmall fraction of its imtial cross section,because thenv the original inequalities in the wire previous to tchemical reduction become itself, If, forv example; the wire comingrominent, even without the produc tion 0 inequalities bythe chemicalprocess from the die is'"100/1000 mm.- thick at one. I

end and 101 1000 mm. thick at theother (as a may'result from theenlargement of the die 3 by wear during the drawmg of the wire),

so u 105 I 1 te dilferences relative y greater when the wire is brought1301a smaller diameter-for example, to Q 30/1000 mm. For whereas theinequality at first amounted to 1% of the diameter, at the end .of thechemical-reducing process it will amount to about 3% of the diameter;and the difference in sectional area at the ends of the wire will haveincreased in even.

---greater proportion. It is for these reasons ati'ons may consist of asingle drawing opthat after'having been brought to a certain diameter bydrawin the wire is.advanta-' geously reduced in size chemically, orelec-: tro-chemically, then drawn again to obivate or correct therelatively increased deviation 'incaliber, and then once more subjectedto the chemical reducing process. This alternation of the stepsof theprocess may be carried out as often. as desired until the desiredfineness of the wire is attained. The drawingwhich takesplacebetweeneach two chemical or electro-chemical reducing opereration or ofa plurality of such operations; and the process. may in general be soconducted that the available diamond dies shall be utilizedfto the bestadvantage. If, for

; example, a large numberof dies with the diameter-ahave accumulated inthe course of work. and there is a deficiency of dies with a larger; orsmaller diameter 1), then the chemical or .electro-chemical reductionwill be carried 'so far that after it the dies may be used which areavailable in the greatest number. Thus not only is there a reduc tion inthe work of drawing, but also an economy of stones.

My invention'wfllbest be understood in connection with the accompanyingdrawing which may 40 which; illustrates 1 one form of apparatus"vention, and in wh ch v Figure 1 is a longitudinal section of'theapparatus; and Fig. 2 is a transverse section along the line'22 of Fig.1.

Inthe description (presently to. be given) of how the chemical reductionin size may be effected, I have referred to the wire treat ed as so farreduced by the prior mechanical working that the chemical reductionmaybe carried out uninterrupteduntil the wire is brought to the finalsize, according. to the" mode of employing my invention first abovereferred to. Before entering upon this description, I desire to callattention to certain facts, the lmowledge of which may be gen- 'erallyserviceable in the carrying on of my process. I p

It is necessary that the mechanical working result in the breaking up ofthe crystalline structureof the metal. If a' tun en wire of this'sortwhich has been. drawn own to about 5/100 millimeters or less issubiectedto a glowing operation, it will. generally change its structureagain after a longer or shorter time and become c 'stallme,' usually ina few seconds. In this changed,

be used in carrying out my n1 amazes recrystallized condition, thesecond part of the process cannot be carried out with success; foralthough with suitable chemicals corrosion readily takes place, it doesnot go on uniformly, but scales out the crystals and attacks diflerentplaces between the crystals with different intensity, and gives anuneven product of very irregular cross-section,

'with projecting crystal-points and; edges, deep indentations andcracks-,in a word,

an unserviceable product. Again, if a tungsten-wire is made, forexample, by drawing a nickel-tungsten alloy into wire and expelling thenickel by heating in an inert gas or in vacuum, a uniform slender-wirecannot be obtained therefrom by corrosion, since Wire produced in thisway is attacked very irregularly in consequence of its crystallinestructure. It will, therefore, be seen that the absence of thecrystalline structure is a fundamental condition for the production ofthis very fine wire. I may now proceed to indicate in. some detail howthe chemical reduction in size ma be effected.

After the completion of the-mechanical working in aglowing condition andthe drawing to about 5/100 to3/100 millimeters,

the wire may for the further reduction in,

line solution offerro-cyanid of potassium (red'prussiate of potash),-which is used in 'astate of considerable dilution in order to allow thecorrosion to go on slowly, because then the time whenthe process shouldbe stopped in order to obtain the desired di-.

ameter can be gaged much more easily than if concentrated solutionswhich act. too rapidly are employed. Instead of the ferrocyanid ofpotassium solution, the most widely different; alkaline oxidizing meansmay be used,--as,- for example, persulfates, 1

peroxide, etc. Potassiumpermanganate may also be used, especially ifprovision is made in a suitable manner for removing the coatings ofmanganese which precipitate on the wire. 'It is very advantageous topass the .wire throu h an. alkaline bath at a uniform rate. By t e speedof passage the rapidity of the corrosion and consequently the diameterthat will be obtained are determined.

It is not necessary to put oxidizing means in the bath; the chemicalreduction in size may also beefie ct'ed electrolytically. In this casethe tun the anode.

en wire must, of course, forme w reis' passed through the As .tungwireis passed through an ammonia s'olubath at a slow, uniform rate and isproperly to be taken over quite a large number of like polessfianodes)in such a manner that cient contact with them for curthere is rent to besupplied at various points on the wire, since by reason of thevery smalldiameter of. the wire potential difierences otherwise ariselwhich maycause a lack of uniformity'in the corrosion (though this tendency-ischecked by the uniform rate of passage through the bath); The wire may,for example, be alternately taken vertically into the bath and out againin a rising and descending (zigzag) line, andoutside the vesselit mayrun over a number of contacts (anodes)-,rollers for -example,-whichsup'-= I ply the positive current, so that uniform eatmg away of therelatively short loops which are in the liquid between each two rollersis insured. The loops are advantageously stretched in the bath overrollers, for example, which are non-conductors 'of electriclty, or wh chconsist of metal for which the voltage employed is not suficient toenable current to pass into the'liquid. The series'or row of contacts bywhich current issuppliedto'the wire duringits passage through the" bathmay be 'in parallel electrically. Tlmgsten wire without crystallinestructure can also be reduced in gases, as chlorin for example,if thetemperature is maintained .sufliciently high to volatilize the chloridformed. p

To describe anexample' of how the chemibe carried out electrolyticallyfor sizes smaller than those above specifically referred to, '1-1/2 mil.drawn tungsten wire that is, wire of a diameter of one and onehalfone-thousandths of an inch-is passed through a dilute ammonia solution(20 parts concentrated 'ammonia to 80 parts water) at the rate of about160 feet per hour. The

- apparatus illustrated inthe drawing is suitover suitably separatedcylinders 12' and 13 arranged one above theother onan insulat ng frame14 of ebonite or similar material,

able for carrying out this operation. The

tion containedin a' tin box 11 which serves as cathode for a current of0.29 amperes and 2 volts of which thetwire is anode. The wound back andforthin ten loops about to seven feetlof wire being 'in the solution atonce. u The lower roll 12' is made of glass, and the upper roll 13 ismade with longitudinal or'bars15' on the surface so that the points ofcontact between the roll.

and the filament are electrically in parallel,

the contacting metal portions 15 being of platinum iridium. Current isled to the bars t ough afconducting core wand-conducting bearing 17 towhich the positive ole of the battery is connected. By a sing e passageof 1-1/2 through the solucal reduction treatment of the wire may maycyanid of potassium) is verysuitable, or

tion under these conditions it will be reducedto a size of about onemil. or one one-thousandth of an inch. 4 The tungsten wire which is thesubject of my invention finds the most diverse applications. As itstensile strength and also its resistance to heat andto acids isverycon-- siderable, it may serve for suspensionwires for fine measuringinstruments (single and double-wire balances), torsion instruments ofany kind, for. reticles in-optical instru-" ments, andfinally (as abovereferred to) for illuminating bodies for electric incandescent lampsand' the like.- 7

When the fine tungsten wire to be used in. incandescent lamps, it mayafter drawing to 5/100 to 3/100 mm. (for example) be placed upon theusual supporting means l of the lamp,which may have the form of the wellknown supporting frame used in tantalum'lamps and then put in the bathcontaining chemicals adapted by their action to reduce the wire in sizeuniformly, I

"so that a more slender wire of uniform surface and uniformcross-section throughout may result. On account of the material of theholders and the conducting wires, the reduction will in practice not becarriedon'in an acid. solution, since only the strongest oxidizing acids(as concentrated nitric acid) act on the tungsten filament. Such acourse is not necessary, however, since alkaline I solut1ons are verywell adapted to produce auniform reduction; A dilute alkaline-solution.of 'red prussiate of potash (ferrolow the constantly changingelectrical resistance of the filament.- Thus the mounted filamentmaybedipped in a solution of potas sium ferricyanid or potassiumferro-cyanid(about a-5-10% solution) until itscoldre- 1 sistance is doubled, whichtakes about fiveminutes. e o

The. chemical reduction in size may also be performed in a bath whichitself does not attack the tungsten if'tlie tungsten wire is .madethe'anode and a very weak current of a few milliamperes or evenfractions thereof is conducted throu h the bath for aconsiderable time.Regar must be had for the fact that the resistance of the tungsten wireis so great that-with stronger currents the cur.- rent must be suppliedat different points in: order to avoid an irregular reduction.Th'ough-in describing above how my invention can be carried out andapplied. I

have referred to tlmgsten'wire' tungsten rib- 1 a can of coursebe..produeed'-in a similar manner. Such ribbonhas many uses more or IGSSllkQthOSfi of tungsten w1re.

What I claim asnew and desire to secure by Letters Patent of the UnitedStates, is

1. The method of producing very fine tungsten wire of uniform surfaceand crosssectlon which consists in reducing the size of slender tungstenwire free from the-ordinary crystalline structure of tungsten byelectrolytic corrosion..

2. The method of producing very fine re-' fractory metal wire of uniformdiameter and surface which consists in subjecting slender wire that hasbeen deprived of its crystalline structure electrolyte.

3. The method of producing very fine tungsten wire of uniform diameterand sur-' face which consists in electrolytically cor roding slendertungsten wire which has been deprived of its crystalline structure by'mechanical working while hot by passing it at a uniform rate-of speedthrough an alkaline bath as anode in such a mannerfthat a considerablelength of wire is in the bath while supplying current to thewire at anumber of points from a plurality of electrically parallel anodecontacts traversed by the by mechanical working to electrolysis, asanode in a bath of suitable,

wire in its passage through the bath, so as to obtain a uniformcorrosion.

4:. The method of producing very finetungsten-wire, the metal of whichhas been 'tungste'n wire of uniform diameter and surg fa ce: whichconsists in reducing the size of a 35.

deprived of its crystalline structure by mechanical working while hot bysuccessive stages of electrolytic corrosionwith suitable magnificationof the inequalities" of thewire resulting from this electrolyticreduction in size by drawing'Yof the wire between the stages ofthe'electrolytic treatment.

:5. The process of producing very fine A tungsten wire of uniformsurface-andcrosssection which consists in repeatedly hotelectrolyte, and-Counteracting the relative. 40

working a body of tungsten to change it's I structure from crystallineto fibrous and at the'same time to reduce its cross-section andthenfurther reducing its cross-section by

